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Publication Index: WoSSubject: C22

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Now showing 1 - 3 of 3
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    Article
    Citation - WoS: 2
    Citation - Scopus: 1
    Comparison of the Performance of Structural Break Tests in Stationary and Nonstationary Series: a New Bootstrap Algorithm
    (Springer, 2024) Camalan, Ozge; Hasdemir, Esra; Omay, Tolga; Kucuker, Mustafa Can
    Structural breaks are considered as permanent changes in the series mainly because of shocks, policy changes, and global crises. Hence, making estimations by ignoring the presence of structural breaks may cause the biased parameter value. In this context, it is vital to identify the presence of the structural breaks and the break dates in the series to prevent misleading results. Accordingly, the first aim of this study is to compare the performance of unit root with structural break tests allowing a single break and multiple structural breaks. For this purpose, firstly, a Monte Carlo simulation study has been conducted through using a generated homoscedastic and stationary series in different sample sizes to evaluate the performances of these tests. As a result of the simulation study, Zivot and Andrews (J Bus Econ Stat 20(1):25-44, 1992) are the best-performing tests in capturing a single break. The most powerful tests for the multiple break setting are those developed by Kapetanios (J Time Ser Anal 26(1):123-133, 2005) and Perron (Palgrave Handb Econom 1:278-352, 2006). A new Bootstrap algorithm has been proposed along with the study's primary aim. This newly proposed Bootstrap algorithm calculates the optimal number of statistically significant structural breaks under more general assumptions. Therefore, it guarantees finding an accurate number of optimal breaks in real-world data. In the empirical part, structural breaks in the real interest rate data of the US and Australia resulting from policy changes have been examined. The results concluded that the bootstrap sequential break test is the best-performing approach due to the general assumption made to cover real-world data.
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    Article
    Citation - WoS: 1
    Citation - Scopus: 1
    A Unit Root Test With Markov Switching Deterministic Components: A Special Emphasis on Nonlinear Optimization Algorithms
    (Springer, 2023) Omay, Tolga; Corakci, Aysegul
    In this study, we investigate the performance of different optimization algorithms in estimating the Markov switching (MS) deterministic components of the traditional ADF test. For this purpose, we consider Broyden, Fletcher, Goldfarb, and Shanno (BFGS), Berndt, Hall, Hall, Hausman (BHHH), Simplex, Genetic, and Expectation-Maximization (EM) algorithms. The simulation studies show that the Simplex method has significant advantages over the other commonly used hill-climbing methods and EM. It gives unbiased estimates of the MS deterministic components of the ADF unit root test and delivers good size and power properties. When Hamilton's (Econometrica 57:357-384, 1989) MS model is re-evaluated in conjunction with the alternative algorithms, we furthermore show that Simplex converges to the global optima in stationary MS models with remarkably high precision and even when convergence criterion is raised, or initial values are altered. These advantages of the Simplex routine in MS models allow us to contribute to the current literature. First, we produce the exact critical values of the generalized ADF unit root test with MS breaks in trends. Second, we derive the asymptotic distribution of this test and provide its invariance feature.
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    Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Re-Examining the Real Interest Rate Parity Hypothesis Under Temporary Gradual Breaks and Nonlinear Convergence
    (Springer Heidelberg, 2023) Hasanov, Mubariz; Omay, Tolga; Abioglu, Vasif
    This paper investigates the real interest parity hypothesis by testing stationarity of real interest rate differentials for 52 countries with respect to the USA. Taking account of the fact that both asymmetric adjustment and gradual temporary breaks may better characterize the dynamics of real interest rate differentials, we propose a new test that allows for two temporary shifts together with asymmetric adjustment towards the equilibrium. We employ the newly proposed test procedure along with the conventional ADF test as well as nonlinear KSS and OSH tests to examine stationarity of real interest rate differentials. Among the main results, we find that the newly proposed unit root test procedure highly outperforms the existing unit root tests in terms of rejecting the null hypothesis of unit root. Our results suggest that real interest rate differentials can be characterized by a stationary process with asymmetric adjustment around gradual and temporary shifts of mean.